Atlus titles tend to disappear quickly so if you are looking for future cash, I would suggest titles by them. I'm not sure about Persona 1 for the PSP though in this regard... It doesn't seem like it was well received here in the West after so many people got accustomed to P3/P4. The game is incredibly old school and an early pre-VII PS1 rpg to boot. A physical copy comes with the games soundtrack though.

The others you could probably download but some of them can be found for pretty cheap as physical copies and you might need that cause it will get expensive buying memory sticks that can hold the titles.